I started my car today and it had a very uneven idle...it then settled down and then the Check Engine light came on when I was at a stop light. Then when I accelerated, the Check Engine light went off. It stayed off for a while and the idle calmed down and steadied. then about ten minutes later at a stop light the uneven idle started up again and the Check engine light came on again. I am going to take it into the shop tomorrow, but I am using a new mechanic and would love to be able to point him in the right direction. Also, when the check engine light goes on, does it usually indicate anything in particular, or could it be ANYTHING in the engine? It is a 1994 318is that I bought 6 months ago with 118,000 miles on it. I have driven it about 4,000 so far with no problems. Any ideas would be greatly appreciated.
there are sooo many possibilities. hopefully they will be able to hook it up to a diagnostic and find out what is wrong... theres a lot of reasons for a uneasy idle, mine does it because of my sparkplugs. but there are many other reasons
your car has one o2 sensor.. could be the sensor, a cloged vacuum hose, dirty idle control valve,spark plugs... those are the most common things to check. when I was having this issue, ended up being a blocked vacuum hose.
worst case scenario you have engine blowby which is a sign of a failing cylinder or low compression
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